This is flat wrong. The Emancipation Proclamation was drafted in late 1862, the second year of the war when things were very much in doubt. Lincoln issued it in the wake of the major battle at Antietam, which was a brutal "tie" and the deadliest day in American history. The tactical purpose of the Proclamation to try to recapture the momentum and make it clear that the North was now on a path of total war with the South.